Restrict the set of things that const stability can be applied

Remove the custom special case rejecting const stability on macros as it is now handled by the general check

Author: oli-obk

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -243,7 +243,20 @@ impl<S: Stage> AttributeParser<S> for ConstStabilityParser {
             this.promotable = true;
         }),
     ];
-    const ALLOWED_TARGETS: AllowedTargets = ALLOWED_TARGETS;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Fn),
+        Allow(Target::Method(MethodKind::Inherent)),
+        Allow(Target::Method(MethodKind::TraitImpl)),
+        Allow(Target::Method(MethodKind::Trait { body: true })),
+        Allow(Target::Impl { of_trait: false }),
+        Allow(Target::Impl { of_trait: true }),
+        Allow(Target::Use), // FIXME I don't think this does anything?
+        Allow(Target::Const),
+        Allow(Target::AssocConst),
+        Allow(Target::Trait),
+        Allow(Target::Static),
+        Allow(Target::Crate),
+    ]);
 
     fn finalize(mut self, cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
         if self.promotable {

compiler/rustc_expand/messages.ftl

@@ -87,11 +87,6 @@ expand_macro_call_unused_doc_comment = unused doc comment
     .label = rustdoc does not generate documentation for macro invocations
     .help = to document an item produced by a macro, the macro must produce the documentation as part of its expansion
 
-expand_macro_const_stability =
-    macros cannot have const stability attributes
-    .label = invalid const stability attribute
-    .label2 = const stability attribute affects this macro
-
 expand_macro_expands_to_match_arm = macros cannot expand to match arms
 
 expand_malformed_feature_attribute =

compiler/rustc_expand/src/base.rs

@@ -979,12 +979,6 @@ impl SyntaxExtension {
         let stability = find_attr!(attrs, AttributeKind::Stability { stability, .. } => *stability);
 
         // FIXME(jdonszelmann): make it impossible to miss the or_else in the typesystem
-        if let Some(sp) = find_attr!(attrs, AttributeKind::ConstStability { span, .. } => *span) {
-            sess.dcx().emit_err(errors::MacroConstStability {
-                span: sp,
-                head_span: sess.source_map().guess_head_span(span),
-            });
-        }
         if let Some(sp) = find_attr!(attrs, AttributeKind::BodyStability{ span, .. } => *span) {
             sess.dcx().emit_err(errors::MacroBodyStability {
                 span: sp,

compiler/rustc_expand/src/errors.rs

@@ -85,16 +85,6 @@ pub(crate) struct CollapseMacroDebuginfoIllegal {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(expand_macro_const_stability)]
-pub(crate) struct MacroConstStability {
-    #[primary_span]
-    #[label]
-    pub span: Span,
-    #[label(expand_label2)]
-    pub head_span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(expand_macro_body_stability)]
 pub(crate) struct MacroBodyStability {

tests/ui/attributes/const-stability-on-macro.rs

@@ -2,13 +2,13 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 #[rustc_const_stable(feature = "foo", since = "3.3.3")]
-//~^ ERROR macros cannot have const stability attributes
+//~^ ERROR attribute cannot be used on macro defs
 macro_rules! foo {
     () => {};
 }
 
-#[rustc_const_unstable(feature = "bar", issue="none")]
-//~^ ERROR macros cannot have const stability attributes
+#[rustc_const_unstable(feature = "bar", issue = "none")]
+//~^ ERROR attribute cannot be used on macro defs
 macro_rules! bar {
     () => {};
 }

tests/ui/attributes/const-stability-on-macro.stderr

@@ -1,20 +1,18 @@
-error: macros cannot have const stability attributes
+error: `#[rustc_const_stable]` attribute cannot be used on macro defs
   --> $DIR/const-stability-on-macro.rs:4:1
    |
 LL | #[rustc_const_stable(feature = "foo", since = "3.3.3")]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid const stability attribute
-LL |
-LL | macro_rules! foo {
-   | ---------------- const stability attribute affects this macro
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: `#[rustc_const_stable]` can be applied to associated consts, constants, crates, functions, impl blocks, statics, traits, and use statements
 
-error: macros cannot have const stability attributes
+error: `#[rustc_const_unstable]` attribute cannot be used on macro defs
   --> $DIR/const-stability-on-macro.rs:10:1
    |
-LL | #[rustc_const_unstable(feature = "bar", issue="none")]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid const stability attribute
-LL |
-LL | macro_rules! bar {
-   | ---------------- const stability attribute affects this macro
+LL | #[rustc_const_unstable(feature = "bar", issue = "none")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: `#[rustc_const_unstable]` can be applied to associated consts, constants, crates, functions, impl blocks, statics, traits, and use statements
 
 error: aborting due to 2 previous errors